Stress-induced anterior displacement of the rabbit temporomandibular joint disc and expression of NF-κB and its downstream inflammatory factors

Objective To establish an animal model of anterior displacement of the temporomandibular joint disc in rabbits and observe the pathological changes of condylar cartilage under stress by using HE staining, immunohistochemical staining and immunofluorescence staining. Methods Thirty adult New Zealand white rabbits were randomly divided into a Sham operation group and four experimental groups, with six rabbits in each group. The Sham operation group underwent a sham operation, while the experimental groups were used to establish an animal model of anterior displacement of the temporomandibular joint disc. The experimental groups were further divided into a model group (no postoperative treatment), a 2-APB (TRPM7 inhibitor) group, a PDTC (NF-κB specific inhibitor) group, and a Diclofenac group. Two weeks after the operation, the experimental animals were sacrificed, and pathological sections of the condylar cartilage were made. HE staining was used to observe the pathological changes of the condylar cartilage, and immunohistochemical staining and immunofluorescence staining were used to observe the expression of NF-κB and its inflammatory factors. Results ① HE staining showed that the pathological changes of the condylar cartilage were obvious at the 2nd week. Compared with the 2-APB group, PDTC group, and Diclofenac group, the pathological changes in the model group were more obvious. ② Immunohistochemical staining showed that the expression of TRPM7, NF-κB, IL-1, IL-6, TNF-α and MMP-3 in the model group was higher than that in the sham operation group. After treatment with 2-APB, PDTC or diclofenac, the expression of TRPM7, NF-κB, IL-1, IL-6, TNF-α and MMP-3 decreased. ③ Immunofluorescence staining showed that the expression of NF-κB in the model group was higher than that in the sham operation group. After treatment with 2-APB, PDTC or diclofenac, the expression of NF-κB decreased. Conclusion ① Under stress, the condylar bone undergoes early remodeling, and the apoptosis of condylar chondrocytes increases with the extension of loading time within a certain period. ② Diclofenac, 2-APB and PDTC can all reduce the apoptosis of condylar cells, and inflammatory factors also play an important role in the apoptosis of condylar chondrocytes.